Assembly and method for installing and retaining valve seals

ABSTRACT

An assembly for retaining a seal ring in a seating surface of a valve is provided having a circumferential groove disposed in the seating surface for receiving the seal ring. The groove has a pair of substantially opposed side walls, one of which includes a first retention member extending into the groove. The opposite side wall is provided with a circumferential slot which is accessible from outside the valve sealing surface through a passage. A second circumferential retention member is inserted into the slot throughout the passage and protrudes into the groove such that both retention members cooperate to retain the seal ring within the seating surface.

This is a continuation of co-pending application Ser. No. 883,699 filedJuly 9, 1986, now U.S. Pat. No. 4,779,841.

FIELD OF THE INVENTION

The present invention relates to sealing mechanisms and moreparticularly to improved seal ring retention assemblies and methodswhich permit easy installation and replacement of seal rings.

BACKGROUND OF THE INVENTION

The sealing of adjacent valve surfaces against fluid flow is commonlyaccomplished by means of a seal ring disposed within a groove or channelformed in one of the valve surfaces. Valves generally have some form ofretention assemblies for retaining the seal in the sealing surface. Suchretention assemblies, however, not only increase the cost of the valvebut, under certain operating conditions, can actually compromise thevalve's performance. This is especially true for valves which arerequired to withstand extreme conditions of temperature and pressuresuch as, for example, in High Performance Butterfly Valves (HPBV). Thesubsequent discussion is directed to specific applications in HPBV asbeing exemplary of other valves in the art and is not intended to be alimitation on the application of the invention.

Various designs have been used for retaining the seal members within agroove in a sealing surface of the valve even under adverse operatingconditions. An example is shown in U.S. Pat. No. 3,642,248, issued toRobert E. Benware and owned by the assignee of the present invention.Benware discloses a valve sealing mechanism wherein a seal ring isconfined in an undercut circumferential groove. These seal rings areusually composed of a resilient material having the ability to deformand reform to their original shape. They are provided with a pair oflongitudinal shoulders which are engagable with opposing flanges formedin the circumferential groove.

An optional backing ring may be used to force the shoulders of the sealring to abut the flanges formed in the groove. This backing ring servesthe dual function of urging the seal ring out of the groove into firmcontact with the sealing surface and of sealing against leakage of fluidunder pressure behind the seal ring.

Installation of seal rings within a groove has heretofore beenaccomplished in different ways. For example, installation can beaccomplished by temporarily deforming the seal ring and inserting itbetween the retaining flanges and into the groove. Once in place, itreforms and is retained in the groove by the retaining flanges abuttingor aligning with the longitudinal shoulders of the seal ring.

It will be understood, however, that if the seal ring is designed sothat it can be readily inserted into the groove, then it is possible forit to be pulled out when the seal ring is placed under severe operatingconditions by high velocity fluids. This possibility of extraction iscaused by a low pressure region created as the fluid flows past the sealring at high velocity. The low pressure region creates a vacuum over theseal ring and acts to draw it into the flow stream. Theoretically itmight be possible to design a seal ring so that it seats into a groovesufficiently tight to prevent it being drawn out by the low pressureregion. However, this would require special equipment to install therings and there is an increased risk of damage to the ring duringinstallation.

Valves also have been provided with separate seal retaining ringassemblies which either cover the full raised face of the valve or arethe screwed-on type which partially cover the valve face. Theseassemblies generally permit much closer clearances between the retainingrings and the seal rings and, further, permit the use of non-deformableseal rings of various compositions. They do, however, possess thedisadvantage of having an inherent leak path created by the separateretaining ring.

In the case where a separate full face cover is provided, the leak pathto the outside of the valve is formed at the interface between theretaining flange and the sealing face of the valve housing. To blockthis leak path, separate gasket materials can be incorporated betweenthe retaining ring and the valve body. In the screwed-on type retainingring assembly, the creation of the leak path is further compounded bythe attachment screws which interrupt the sealing face of the valve.This interruption increases the possibility of flange gasket failure.

Where a separate retaining ring assembly is used, installation and/orreplacement of seal rings is complicated. The retaining ring and gasketseal must be removed, usually necessitating complete removal anddisassembly of the valve.

In each of the methods discussed above, particular consideration must begiven when the valve is used under dead-end service conditions. Theseconditions occur when a valve is placed under pressure on one side ofthe sealing surface while the piping is removed from the opposite side.Where this occurs, the retainer assembly is exposed and must support aportion of the extreme pressure exerted on the valve sealing surface.

OBJECTS AND STATEMENT OF THE INVENTION

It is therefore an object of the present invention to provide animproved seal retention assembly which permits an uninterrupted gasketface on the valve without creating an additional leak path.

It is another object of the present invention to provide an improvedseal retention assembly which does not require a removable retainer orits fasteners to support loads in dead-end service valves.

It is a further object of the present invention to provide an improvedseal retention assembly which securely retains the seal ring and can beinstalled and/or removed without the need for special equipment ordisassembly of the valve.

It is another object of the present invention to provide a method foreasily and efficiently installing and/or removing a valve seal utilizingthe present improved seal retention assembly.

These objects and others are accomplished by the present invention andparticular embodiments of this invention are described herein below.

In one advantageous embodiment employing the present invention, a firstmember which is to be sealed with respect to a second member is providedwith a circumferential groove which is shaped so as to cooperate with aslidable retaining member to maintain a seal ring in operable position.

The seal ring used with the present invention can be of any appropriateshape or material necessary for the desired application. Exemplary sealrings are those having a body formed with longitudinal shoulder portionsas described in U.S. Pat. No. 3,642,248.

In applications wherein tight sealing is not required, the seal ring maybe in the form of a split ring or even formed in a plurality of segmentsfor installation in the groove. This is particularly advantageous wherethe seal is best formed of a brittle material such as graphite whichwould not be insertable in one continuous piece.

The groove is provided with an undercut side wall so as to provide anoverhanging portion forming a first retaining flange or lip. This firstretaining flange is engagable with one shoulder of the seal ring. Anannular slot is formed in the side wall opposite the first retainingflange. The annular slot is accessible from either inside the flowchamber of the valve or outside the valve housing as desired through apassage formed in the housing. That passage is dimensioned to permit aretention member to be inserted through the passage and into the annularslot. Once the seal ring is properly seated into the groove, thisretention member is inserted through the passage to fill the annularslot. The retention member is held in the annular slot and extends intothe circumferential groove to form a second retention flange forengaging the seal ring to insure secure and efficient retention of theseal ring within the groove. This effectively prevents the low pressureregion created by the passage of fluid at high velocity discussed abovefrom drawing out the seal ring into the fluid flow.

Utilizing this method and assembly, a wide variety of materials may beutilized in forming the seal ring. There is no requirement that thematerials be capable of deforming to pass between and fit within theconfines of a pair of restricted retention flanges. It is only necessarythat the seal be capable of passing through a smaller diameter openingto reach the cavity. This can be accomplished by segmenting the sealring or by splitting the seal ring to permit insertion. Alternatively,the seal ring can be formed of a material sufficiently deformable topass, in one piece, through the smaller diameter opening to reach thecavity. Also, by utilizing the present invention, the seal ring can beeasily removed and replaced without requiring complete disassembly ofthe valve.

The foregoing and other objects, features and advantages of the presentinvention will become apparent from the description of preferredembodiments in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view, in cross-section, of a PRIOR ARTscrew-type sealing flange assembly for High Performance ButterflyValves;

FIG. 2 is a side elevational view, in cross-section, of a PRIOR ARTsolid sealing flange assembly for High Performance Butterfly Valves;

FIG. 3 is a side elevational view, in cross-section, of a PRIOR ARTgroove and wear ring assembly in accordance with the Benware patent.

FIG. 4 is a perspective view, in section, of one embodiment of theretention strip of the present invention;

FIG. 5 is a sectional side elevational view, in cross-section takenalong line 5--5 of FIG. 3, of the retention strip of one embodiment ofthe present invention;

FIG. 6 is a side elevational view, in cross-section taken along line6--6 of FIG. 4, of the retention strip, wear ring, and backing ring inoperable position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to the drawings and, in particular, to FIGS. 1-3, thereare depicted three (3) embodiments of PRIOR ART sealing and seal ringretention assemblies. Though these PRIOR ART devices are shown in theirapplication to High Performance Butterfly Valves (HPBV), for thepurposes of the present invention their design and usage is similar inother applications.

FIG. 1 shows a typical "screwed-on" type flange sealing apparatus inaccordance with the PRIOR ART. The valve body 20 has a portion of acircumferential groove 21 formed or cut therein for placement of a sealring (not shown). This seal ring is held within the groove 21 by aseparate circumferential sealing flange 22 which is maintained inabutment with valve body 20 by means of a plurality of retaining screws24. After the seal ring, sealing flange 22 and retaining screws 24 arein position, a second annular resilient seal 26 is interposed betweenvalve body 20 and circular retaining block or pipe flange 28. Thissecond seal 26 is held in place by means of a circular retaining block28, which block is placed in compression by a plurality of bolts 30.

As shown in FIG. 1, the use of this assembly forms a potential leak pathas indicated at arrow 32 for high pressure fluid to escape the sealingassembly and vent to the outside of the valve body or into thedownstream side of the valve. The sealing assembly further includes aplurality of interruptions formed in sealing flange 22 by the placementof retaining screws 24.

The sealing assembly of FIG. 2, shown generally at 38, demonstratesanother example of the PRIOR ART. A valve body 36 is placed in abutmentwith circumferential flange 38, which together form the circumferentialgroove 40 for the seal ring (not shown). An annular seal 42 isinterposed between a retaining block or pipe flange 44 and sealingflange 38 in order to maintain the close clearances between said flangeand valve body to prevent fluid leakage. The resilient seal 42 ismaintained in compression by tightening bolt 46 to the desiredspecifications.

This configuration, while eliminating the interruption in the sealingflange created by the retaining screws in the assembly of FIG. 1, doesnot eliminate the potential leak path (shown by arrow 48) which isinherently formed at the interface between sealing flange 38 and valvebody 36. These potential leak paths can exist in both of the PRIOR ARTembodiments utilizing the sealing assemblies shown in FIGS. 1 and 2.

FIG. 3 shows another PRIOR ART embodiment which incorporates a separatecircumferential sealing assembly disposed in the valve body 54. Thisassembly comprises an undercut, circumferential groove 52 having twooverhanging flange members (56 and 58) which are intended to maintainseal ring 60 within the groove 52. This arrangement, however, requires aseal ring capable of being substantially deformed so as to permitinsertion within groove 52 and yet rigid enough to prevent seal ring 60from being extracted from groove 52 when placed in operation underconditions of high velocity fluid.

Referring now to FIG. 4 an embodiment of the present invention is shown.Valve housing 72 includes a circumferential groove 70 for receiving aseal ring 74. This groove 70 (best shown in FIG. 6) includes a pair ofsubstantially opposed side walls 91 and 92. Side wall 91 is undercut soas to provide an overhanging flange portion 76. Flange portion 76 ispositioned so as to be engagable with a circumferential longitudinalshoulder 78 formed in seal ring 74. An annular slot 80 is provided inthe groove side wall 92 opposite overhanging flange portion 76. Thisslot 80 is dimensioned to maintain a retaining strip or member 82. Inits proper position in slot 80, retaining strip 82 extends into groove70 for engaging a circumferential longitudinal shoulder 84 formed inseal ring 74. The retaining strip is preferably flexible and can be madefrom any appropriate material including but not limited to Teflon (atrademark of E. I. DuPont DeNemours & Co. for a polymer oftetrafluorethylene), Tefzel, (a trademark of E. I. DuPont DeNemours &Co. for synthetic resinous Fluorine-containing polymers), nylon,stainless steel or any of the nickel based alloys such as the Inconels(a trademark of International Nickel Company, Inc. for nickel alloys andalloys of nickel, chromium and iron).

Access to slot 80 is provided by a passage 86 formed in valve body 72.This passage 86 permits the insertion of retaining strip 82 from insidethe flow chamber of the valve after seal ring 74 has been positionedwithin groove 70. The passage 86 may, alternatively be formed fromoutside the value body 72 depending upon the desired application.Passage 86 also permits easy removal of retaining strip 82, for exampleby means of a standard needle nose pliers.

Seal ring 74 may be provided with a circumferential channel 87 formed inits rear surface to receive a backing ring 88 which is in contact withthe floor 93 of circumferential groove 70. This backing ring 88 providesa supplementary sealing surface between the seal ring 74 and the base 93of the circumferential groove 70. It also serves to bias seal ring 74away from the circumferential groove and maintain seal ring 74 in closerproximity to or against retaining flange 76 and the retaining surfacewith the valve disc 94.

A particularly advantageous method for installing and retaining a sealring in accordance with the present invention involves first inserting aseal ring or a seal ring/backing ring combination into the groove asshown in FIG. 6. The ring 74 should be positioned such that overhangingflange portion 76 overlies longitudinal shoulder 78. Once the seal ringis properly positioned, a retaining strip (shown in FIGS. 4 and 5) isslidably inserted into passage 86 and fed around the circumference untilthe slot 80 is sufficiently filled to retain seal ring 74 within groove70 by blocking shoulder 84. The retaining strip need not fill the entirecircumferential length of slot 80 and may alternatively be segmented asdesired. This retaining strip 82 may advantageously be formed inpredetermined lengths corresponding to the circumference of slot 80 ormay be provided in longer lengths which are subsequently cut to size.The retaining strip can also be formed from any appropriate materialcapable of deforming sufficiently for insertion through passage 86 intoslot 80.

The arrangement of the invention provides several advantages over theprior art devices. For example, the seal ring need no longer be formedof resilient material capable of deforming for insertion within aconstricted slot formed in the valve body. This permits the use of awide range of materials tailored to a particular application. Forexample, where absolute leak-proof sealing is not required, as incertain control valves, the seal ring can be formed in sections ofnon-deformable materials as described above. Alternatively, the sealring may be in the form of a split circumferential ring which can beminimally deformed to pass through the smaller diameter opening to reachthe groove 70.

Depending upon the particular application or need, a wide range oftolerances may be used between the seal ring and the circumferentialgroove without requiring special equipment to install or remove the ringand without the resultant potential for damage to the ring duringinstallation. A further advantage of the present invention is that itpermits easy installation and removal of seal rings in the field withoutdisassembling other valve components or requiring complete removal ofthe installed valve. This is easily accomplished by withdrawing one endof the retaining strip from its position in the passage to the annularslot, lifting out the seal ring and inserting a replacement. Once thereplacement is in position, the retaining strip is reinserted throughthe access passage and the sealing assembly is ready for operation.

The foregoing is considered as illustrative only of the principles ofthe present invention and is not limited to the particular embodimentsdiscussed herein. Various changes, substitutions and modifications maybe made thereto by those skilled in the art without departing from thespirit or scope of the invention defined by the appended claims.

What is claimed is:
 1. An assembly for retaining a seal ring in aseating surface of a valve body comprising: a circumferential groovedisposed in the seating surface for receiving the seal ring, the groovehaving a pair of substantially opposed side walls, one of said sidewalls including a first retention means for retaining a portion of theseal ring in the groove, the other side wall including a circumferentialslot, said slot having a pair of spaced apart base surfaces and asidewall surface disposed between said base surfaces, one of said slotsurfaces including a passage therethrough comprising a cut-out along aportion of the circumference of said one slot surface for accessing saidslot; and a second retention means insertable through said passage insaid one surface of the slot and receivable in said slot with a portionof said second retention means extending into the groove such that saidfirst and second retention means can retain the seal ring within theseating surface.
 2. An assembly for retaining a seal ring in a seatingsurface of a valve body as in claim 1 wherein said passage accessingsaid slot comprises a rectangular cut-out formed in said one surface ofsaid circumferential slot.
 3. An assembly for retaining a seal ring in aseating surface of a valve body as in claim 1 wherein said slot extendssubstantially the entire circumference of the groove.
 4. An assembly forretaining a seal ring in a seating surface of a valve body as in claim 1wherein said second retention means comprises a flange member that ispre-cut to the length of said slot.
 5. An assembly for retaining a sealring in a seating surface of a valve body as in claim 1 wherein saidsecond retention means is formed from a strip of flexible material. 6.An assembly for retaining a seal ring in a seating surface of a valvebody as in claim 5 wherein said second retention means is formed ofstainless steel.
 7. An assembly for retaining, in a seating surface of avalve, a seal ring having a shoulder portion which includes two ends,said assembly comprising;a circumferential groove formed in the valveseating surface, said groove having a pair of substantially opposed sidewalls and a base portion, one of said walls further having a firstretention flange member extending into the groove, the opposite sidewall including a circumferential slot, said slot having a top and bottomsurface, said top surface including a passage therethrough comprising acut-out along a portion of the circumference of said top surface foraccessing said slot; and a second retention flange member insertablethrough and removable from said passage and maintainable in said slot,said first and said retention flanges being engageable with the shoulderportion of said seal ring to maintain the ring within the groove.
 8. Anassembly for retaining a seal ring in a seating surface of a valve bodyas in claim 7 wherein the distance between said first retention flangemember and said opposite side wall is greater than the distance betweenthe ends of the shoulder portion of said seal ring when said secondretention flange member is not in place.
 9. An assembly for retaining aseal ring in a seating surface of a valve body as in claim 8 wherein thedistance between said first retention flange member and said secondretention flange member is less than the distance between the ends ofthe shoulder portion of said seal ring when said second retention flangeis in place.
 10. An assembly for retaining a seal ring in a seatingsurface of a valve body as in claim 7 which further comprises a backingring disposed betweens said seal ring and the base of saidcircumferential groove for urging the shoulder portion of said seal ringtoward the first and second retention flanges, and creating a pre-loadwith the sealing surface of the valve.
 11. An assembly for retaining aseal ring in a seating surface of a valve body as in claim 7 whereinsaid passage is accessible from outside the valve body.
 12. An assemblyfor retaining a seal ring in a seating surface of a valve body as inclaim 7 wherein said passage is accessible from the seating surface ofsaid valve body.